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XR 1,806 9871 v EAR-6mm v May 26, 1931. v w. lasowEFe v 1,806,871

SOUND INTENSITY MEASURING SYSTEM i l f v f I Filed Jan. 30. 1929 J I E 524 t 1- I J 22 INVENTOR. WW) 6. iydowev, BY WM Y ATTORNEY in; r i,

Patented May 1931 WARD E. BOWER, OF G'I'ON, DYE/T314351 GI! connima.

SOUND mTEI ISIIY HEABUBINQ BYEITIM A lication med ne so, was. sci-m R0.836,221.

This invention relates broadly to means and apparatus for determinationof characteristics of mechanical vibrations. More par-ticularly thisinvention relates to devices employed in sound analysis.

provide a periodicmechanical vibrator with means for transformingmechanical vibrations into electrical impulses.

A further object of this invention is to provide piezo electric elementsupon surfaces of periodic mechanical vibrators whereby sound wavesimpinging upon the select-ed periodic mechanical vibrator aretransformed into electrical impulses.

Other and further objects and features of this invention will beapparent to those skilled in the art to which this invention pertains.

According to this invention'piezo electric elements are mounted uponelastic menicers of predetermined dimensions. A selector arrangement isconnected to each of the elements for selectively connecting theelements to an amplifying system which is connected to an indicatingdevice. In case very active piezo electric elements are employed inconjunction with a sensitive indicating device the amplifying systemneed not be employed. Among the uses and applications of this inventionare the tuning of musical instruments, such as pianos, determination ofacoustical-efiects in chambers, halls and churches,-the determination offrequency characteristics of audio frequency amplifiers, and thedetermination. of frequency of alternating current powertransmission-systems.

In the drawings Fi ure 1 shows a diagrammatic view of an emfiodiment ofthis invention adapted for general sound measurements; Fig. 2 is across-sectional view with parts illustrated in elevation showing detailsof construction of the periodic mechanical vibrators; and Fig. 3 showsan arrangement of the apparatus of my invention for the determination offrequency of an alternating current power transmission system.

Referring to the drawings in detail, reference numeral 1 designates achannel member which is preferably heavily dam ed and free frommechanical resonating e ects within the audible range of soundfrequencies. Reference numerals 2 and 4 designate the walls of thechannel. member. A protruding member 3 is provided between the walls 2and 4. Elastic rods 5, 5a, 5?), 5c, 5d, 5e, 5; and 59 extend through thewell member 4. These elastic rods may be of any metallic material. Incertain cases, however, elastic rods of insulating material may also beused. The physical dimensions of these rods may be so chosen that theirfrequencies correspond to an octave of the musical scale. Thus the rods5, 5a, 5b, 5c, 5d, 56, 5 and 5g may be made to correspond to the notesof the musical scale designated by C, D, E, F, G, A, B and C, 7respectively. The piezo electric elements 6, 6a, 6b, 6c, 6d, 6e, 6f and69 are mounted upon the vibrating reeds 5, 5a, 5b, 5c, 5d, 5e, 5f and5g, res ctively near the wall member 4. Each 0 these piezo electricelements may be so cemented to the surface of a vibrating reed and thesurface of the reed used as one of the electrodes for the piezo electricelement. Cements having a metallic base, such as sodium or potassiumsilicate may be used to fasten the elements into position upon thereeds. When elastic reeds of insulating material are employed thesurfaces of the piezo el ctric elements adjacent to the reeds are firstcos ted with conducting medium such as gold leaf, finely dividedplatinum or various metal foils. The coatings which are adjacent to thereeds are all connected together into the input circuit of the amplifiersystem'9. Where vibratin reeds of conducting material are employe thereeds themselves serve as one of the electrodes for the piezo electricele ments and the frame member 1 is connected to the input of theamplifier system 9 as indicated at 120.

Coatings are provided on the outer surfaces of the piezc electricelements. Connections between the selector switch 11a contacts 7, 7a,7b, 7c, 7d, 76, 7f and 7g and the respective coatings of the piezoelectric elements are provided. The selector switch 11 is connected tothe input circuit of the amplifier system 9 and provides means wherebyany one of the elements associated with the vibrating reeds may beconnected into the input circuit of the amplifier. Screw members 8, 8a,8b, 8c, 8d, 8e, 8 and 89 are mounted in the member 3 for engagement withthe respective reeds. Adjustments to compensate for the variations inthe effective vibrating length of each of the reeds caused by changes intemperature may be made by means of these screw members. It often may bevery desirable to use the arrangement herein dis; closed in tuning ofmusical instruments, such as a piano in which several different scalesare in use, in such cases the effective vibrating lengths of the reedsmay be readily adjusted by the use of the screw members so that thefrequency of vibration of each of the reeds and the intervals or ratiosbetween the frequencies of the various reeds may be changed tocorrespond to an octave of either the natural or the equally temperedscale. The amplifying system 9 comprises the electron discharge devices10 and 12 coupled together by a transformer 11. Other coupling meanswell known in the art of amplification of electrical oscillations may beemployed in place of that illustrated. Sources of anode current supply16 and 17 are provided for the electron discharge devices 10 and 12. Asource of current supply 15 is provided to furnish a balancing currentfor the microammeter 14 whereby the micrcammeter may be adjusted to itszero position when the amplifier system is functioning but no electricaloscillations are being impressed upon the input circuit.

Successive electrical impulses transmitted to the in ut circuit of theamplifying systern may c more accurately compared when the indicatingmeter 14 is caused to start always at the zero point. A. currentlimiting device 13 which may be a resistance or an impedanoe unit isconnected into the circuit with the source 15 and the meter 14.

In Fig. 2 is shown an arrangement wherein a housing 18, supported by thetripod 19 is provided for the vibrating reed system for preventingextraneous noises from reaching the reeds. The walls of the housing arehighly damped or padded to prevent sounds introduced into the confinedchamber from being sustained. A sound magnifier 20 of the horn type isprovided in the side of the housing for directing sound waves againstthe vibrating reeds indicated generally at 5 whereby deforming forcesare applied to the piezo electric crystal devices represented at 6 andelectrical impulses transmitted throu h the coating 6 and the vibratingreeds to t 0 binding posts 21. Suitable amplifying and or or measuringap aratus is connected to the terminals 21. esonance between the naturalfrequency of the piezo electric crystal devices and sound waves incidentupon the several reeds is indicated by a definite deflection of meter14. If sound energy from any source acts upon any one of the reeds andthe period of the sound energy is equal to that of the reed and itsassociated piezo electric crystal element a definite deflection of themeter 14 will indicate resonance and its relative intensity, accordingto some previous calibration.

If it is desired to employ the reed arrangement herein disclosed infrequency determinations or measurements in connection with powertransmission systems small solenoids 25 which are connected to the powercircuit 26 may be mounted adjacent to the free ends of each of the reedsas shown in Fig. 3. A periodically varying magnetic flux will then reactupon the reeds and cause that reed having a natural period equal to thefrequency of the current in the power circuit to vibrate.

While I have described my invention in some of its preferredembodiments, I desire that it be understood that modifications of thisinvention may be made and that no limitations upon the invention areintended other than are imposed by the scope of the annexed claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

1. A sound analyzer comprising a mechanical vibration member, a constantfrequency electromechanical vibrator carried by said mechanicalvibration member, an electrical impulse amplifying system including anelectron discharge device, an indicating device associated with theoutput circuit of said amplifying system, and connections between saidconstant frequency electromechanical vibrator and said amplifying systemfor actuating said indicating device according to the operation of saidelectromechanical vibrator due to sound waves incident upon saidmechanical vibration member.

2. In a device of the class described, the combination of a mechanicalvibration member, a constant frequency electromechanical vibratorcarried by said mechanical vibration member, an electrical impulseamplifying system including an electron discharge device, connectionsbetween said constant frequency electromechanical vibrator and saidamplifying system, an indicating device connected with the outputcircuit of said amplifying system and means connected with saidindicating device for causing the indicating member of said device to bemaintained at zero when no mechanical vibrations imping upon saidmechanical vibration member, said indicating device operating to measurethe energy generated by said electromechanical vibrator when sound wavesof a frequency to which said electromechanical vibrator and saidvibration member are resonant imping upon said vibration member.

3. In a device of the class described the combination of a mechanicalvibration member,an electromechanical vibrator carried by saidmechanical vibration member, an indicating instrument for indicating theintensity of vibrations impinging upon said mechanical vibration memberthrough the action of said electromechanical vibrator and means fordirecting sound vibrations against said mechanical vibration member forselectively actuating said member and imparting stresses to saidelectromechanical vibrator for the eneration of current for controllingsaid indicating instrument.

d. In a device for measuring the intensity of mechanical vibrations thecombination of means responsive to mechanical vibrations of apredetermined period, an electromechanical vibrator carried by saidmeans, means for directing sound waves against said first mentionedmeans, and an indicating device connected to said electromechanicalvibrator for indicating the intensity of vibration of said first namedmeans when the impressed m chanical vibrations correspond in frequencyto the natural frequency of said electromechanical vibrator.

5. In a device for measuring the intensity of mechanical vibrations thecombinationof a plurality of mechanical vibration members of differentfrequency characteristics, electromechanical vibrators individualotoeach of said members, an amplifier connectible with each of saidelectromechanical vibrators, and indicating means connected with theoutput circuit of said amplifier and operative under control of theelectromechanical vibrator resonant to a particular impressed frequenc6. n a device for measuring the intensity of mechanical vibrations thecombination of a plurality of mechanical vibration members, of differentfrequency characteristics, electromechanicalvibrators individual to eachof said members and corresponding to the frequency thereof, an amplifiersystem having an input and an output circuit, circuit selecting meansconnected to the input circuit of said amplifier system, each of saidelectromechanical vibrators being individually connected to said circuitselecting means whereby a selected one of said electromechanicalvibrators may be connected to said amplifier system and indicating meansassociated with the output circuit of said amplifier system andoperative under control of the electro-mechanical vibrator which isresonant to the particular impressed frequency.

7. In a s stem for measuring the intensity of sound t e combination of apluralit of vibrating reeds of different frequency characteristics,means for supporting said reeds, means for adjusting the length of thevibrating portion of said reeds, piezo electric elements of a frequencycorresponding to the frequency of said reeds mounted upon each of saidvibrating reeds, an amplifying sys tem, connections between said piezoelectric elements and said amplifying system, and indicating meansconnected with the output circuit of said amplifying system forindieating the relative intensities of the sound waves impinging uponsaid vibrating reeds under control of the piezo electric elementsresonant to the frequency of the impressed sound waves.

8. In a s stem for measuring the intensity of sound t e combination of aplurality of vibrating reeds of difi'erent frequency characterics, meansfor supporting said reeds, means for adjusting the length of thevibrating portion of said reeds, a piezo electric element having afrequency corresponding to the frequency of said reeds individual toeach of said vibrating reeds, an amplifying sys tern, means forselectively connecting each of said piezo electric elements to saidamplitying system, an indicating device connected with said amplifyingsymm for indicating the intensity of the sound waves impinging upon saidreeds, and means connected with said indicating device for maintainingsaid device at its zero point exce t when sound waves impinge upon saidrec s for the selective operation of a particular reed and the piezoelectric element associated therewith.

9. In an' apparatus for measuringizhe intensity of sound waves thecombination of a.

plurality of elastic reeds each resonant to a.

selected frequency, means for supporting said reeds, members associatedwith said supporting means and with said reeds for moving said reedswith respect to said supporting means whereby the natural period ofvibration of said reeds may be varied, piezo electric elements mountedupon each of said reeds, said elements having a natural frequencycorresponding to each of said reeds and means for detecting oscillationsgenerated by any one of said piezo electric elements under control ofsound waves incident upon said reeds.

10. In an apparatus for measuring the intensity of sound waves thecombination of a plurality of elastic reeds of different frequencycharacteristics, means for supporting said reeds, members associatedwith said supporting means and with said reeds for moving said reedswith respect to said supporting means whereby the natural period ofvibration ofsaid reeds may be varied, piezo electric elements havingfrequencies corresponding to the frequencies of said reeds and mountedupon each of said reeds, an indicating meter for measuring the energygenerat- 5 ed by the individual piezo electric elements, a cabinet forhousing said reeds for excluding extraneous sounds from said reeds, andmeans for directing sound waves against said reeds for selectivelyactuating a reed corresponding in frequency to the frequency of theimpressed sound waves and controlling said meter by the oscillationsgenerated by the corresponding piezo electric element.

ii. in a system for measuring the intensity of sound waves thecombination of a plurulit y of elastic reeds each having differentfrequency characteristics, means for supporting said reeds. means formovingsaid reeds with respect to said supporting means whereby thenatural period of said reeds may be varied, piezo electric elementscorresponding in frequency to the frequency of said reeds carried byeach of said elastic reeds, a housing for said reeds for excludingextraneous g5 sounds from said reeds, means mounted upon said housingfor directin sound waves against said reeds, an amplifier system,connections between said amplifier system and selected ones of saidpiezo electric elements, and indicating means connected with saidamplifying system and actuated by the energy generated by the selectedpiezo electric element for determining the intensity of the sound wavesimpinging upon said elastic $5 reeds.

WARD E. BOWER.

